Several of us on the list are working with NIM modules and bins in our effort to instrument ourselves for nuclear detection schemes.

What follows is a short history of NIM which while not directly involving fusion will serve to educate others in what it is and how it came to be a standard. I will continuously add to this post as needed.

NIM Nuclear Instrumentaion Module

By the 1950's it was realized that most all nuclear instrumentation utilized several, common, basic building blocks with only a single or couple of application specific items for each different measurement scheme or system.

The idea came to a number of people that the basic building blocks could be provided in portable, removable modules common to a single cage or rack which would itself have a built in power supply to supply 4 commonly used DC and the standard line AC voltages on a bussed together group of standard amp plugs. The cage and attached power supply would itself fit into a standard 19" rack for laboratory use. The standardized modules could then just slide into the rack on rails and the rear mounted power plugs couple into the modules. The modules could then be linked up in logical order via front or back BNC jacks and cables to make any instrument desired. Neat, huh?

The credit for publishing the first paper to standardize this system goes to Lou Costgrell of the old Atomic Energy Commission who authored the document "Standard Nuclear Instrument Modules" TID-20893.

ORTEC (Oak Ridge Technical Enterprise Corp) offered 17 Nim Modules in their first catalog in 1966. Tennelec (Tennessee Electronics) was also an early supplier of NIM modules. (Bought out by Oxford and then Canberra. Most of the NIM makers are or were clustered in a cozy fashion on the door step of the major national AEC laboratories, which were their prime customers.

I need help...Anyone know the letter codes in question marks? Got any Nim Modules made by another maker? Let me know.

ORTEC and Canberra remain the largest suppliers with SRS and a few others hanging in there. Many are gone or have been absorbed. ORTEC is now really part of Perkin Elemer along with the old EG&G.

The NIM bin and its standard slots have also had non-nuclear modules made for it. I have seen, and own, Laser Q switches, pockels cell controllers, and other electro-optical system modules bundled in the Nim module format.

A NIMless future?

With modern computers/laptops becoming a defacto lab standard and modern integrated circuits putting entire, rocket fast, complex systems on a single chip, the large, bulky rack mount NIM system is looking pretty long in the tooth.

Small boxes the size of a pack of cigarttes now plug into the USB port via a cable and you have a complete gamma spectrometer. Jack fields and snarled patch cords are being replaced by software which is multi-faceted and multi-tasking, changing you laptop from a gamma spec. to a mass spec. with a touch of a function key.

NIM is still actively sold, but for how long? A vast amount of surplus NIM is currently on E-bay as one college after another folds up half century old nuclear physics and engineering departments. Others still hanging on are moving into the 21st Century and getting computerized in the lab. (more NIM hittin' th' streets). It is a good time to buy into used NIM.

Nim Connectors/bins/standards......................

"Bin" or NIM frame

This is a rectangular metallic cage designed to mount in the universal 19" professional, vertical, rack mount. When empty, there are 12 slots with 12 guide rails and twelve AMP connector plugs in the rear of the unit designed to interface with an inserted module. The regulation NIM slot width and front plate is 1 3/8" wide. The height is 8 3/4 inches. This latter figure is also the height of the entire bin, thus it takes up about 6R or 6 standard 19" rack unit heights in any rack into which it is installed.

The rear of the bin has a low voltage DC regulated power supply attached. It supplies the following voltages to the following pins on each NIM connector.

The logic highs and lows of the original NIM spec are leftovers from discrete transistor wired logic days and are not generally compatible with modern logic families. The book "Building Scientific Apparatus" has some nice simple interfaces for modern TTL and ECL logic families. For more on the book, check out my post , "Building Physics Instruments" in the Books and References forum.

Output jacks of all nim bins must deliver

logic zero is any voltage between +1volt and -2volts
logic one is any voltage between +4 volts and +12 volts.

All Nim module inputs must accept the following

Logic zero - +1.5 volts to -2 volts
Logic one - +3 volts to +12 volts

You can see there is lots of room for noise immunity and a decent guard band between logic levels. All this makes for fairly slow NIM data rates. (slew rates were low in the old days.) The wide logic level ranges made for relatively easy interfacing.

Inspite of the oddball levels, I have not had to build an interfacing circuit yet for "pulled up", clean, TTL signals.

Connectors......

These are made by AMP corp., and in all NIM Racks, (called NIM bins), they are 90% un-populated. That is, there are not even pins or wires connected to them. The extra pins were here for expansion and individual user use for specific signals to their custom application modules.

For standardizing purposes, all low voltages standardized for NIM use are piped to the same numbered pins on all bins and all modules. These are sacred territory, set in stone, not to be tampered with or altered in any way!

NIM modules do not have to be only 1 NIM slot wide. Complicated modules with lots of circuitry or with bulky or wide meters, readouts, etc are commonly found that takeup 2 or 3 NIM slots. These wider modules, however, must all be a perfect multiple of the standard NIM module width.

Most connectors on the front panel of the modules as well as those on the rear panel, are standard BNC, RF type signal plugs. The standardized impedance of appropriate cables should be 50 ohms. This impedance is common to many instrumentation systems.

Some NIM stuff is 94 ohms (whacko), but 75 ohm cabling can be used provided pulse shape fidelity isn't a major issue.

Some NIM modules, especially single channel analyzers and linear amps, often have a 9 pin "D" standard preamp power plug on the rear panel to power an external preamp. This is normally for a PMT or solid state detector. The pinouts on these for power are fairly standardized, but are not rigidly adhered to across the board. Most are wired as follows

You should check the above pinouts to be sure before pluging in a preamp to avoid problems damaging it or the NIM bin supply. ***NOTE********* Some Tennelec preamps and bins are wired for odd ball 9pin hookups.

More, later.......... check back as I add data.....

Richard Hull

Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Sometimes companies who don't really produce nuclear instrumentation will make a NIM module here or there. For example, I have a 3kv NIM hv supply made by Bertran.

Also, I believe Tennelec was bought by Canberra some time back, and LeCroy recently decided to get out of the modular nuclear instrumentation business. Of course, there are still plenty of their products floating around on the surplus market, and will be for a long time to come.

SRS in particular focuses on supplying high-end specialty modules (boxcar averagers, computer interfaces, etc.) rather than the more general-use products that most other companies in the business are known for. I actually picked up a SRS computer interface module not too long ago (used, of course. The prices new are obscene) It's almost everything I'll need to put my whole fusion setup under computer control.

I had completely forgotten about the other uses for NIM bin platforms. I have several laser related modules on hand (most are now gutted) which were in NIM modules. I have already updated the original post to include this fact.

Thanks. This is the kind of assistance and advice that will see the original post grow in scope and value.

Richard Hull

Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

I liberated some rather old NIM modules from the physics dept at uny which seemed to be early digital stuff, printer interfaces, latches, an aincent video distrobution amp, and loads of custom stuff obviously home-made by the bods in the physics dept some 40 years ago by the look of them. the profesional ones have firnished my with a heap of silver-teflon wire (which seems to be widely used in NIM stuff) i'll check the make tommorow.

if anyone (UK) has a spair bin or PSU around, i am in dire need of one, i have a compleat ortek setup (HVpsu, 2X amps, 2X SCA, 2X rate meter, dual counter, timer) that i aquired when uny decomisioned an old SEM. there rattling around in a modifyed card cage at the moment, and i don't want to have to modify them all and build a psu with all its rather silly (my modurn standards) voltages :/

John,
I've got two somewhat dated Ortec bins, neither have the 6V supply. I have yet to see a module that required 6V, but then again the only modules I'm famliar with are the ones I have, and they're at least 20 years old.

Tks Jon - I had pick it up for a song ( now have two ) but the Voltage cal's were far out. Makes me cringe at the standard of maintenance some of these instruments were subjected too and question the quality of work performed by the so called scientists using them. It has a - 6 v & +6 v but not working - I have identified the 12's & 24's but no sign of 6 -otherwise, bar a bit of metal straightening - I have a useful bin.